Safety baroswitch



April 21, 1959 D. s. WILLARD SAFETY BAROSWITCH Filed Feb. 14, 1958 1 M2; NW 54 UL'HI 4 0'6 WI 7 5 i I I J0 W 1: 49 a i lull l 6 22 3W n DAV/D.$:?FZZ%0 BY Wk add, I" I,

firr wim- United States Patent SAFETY BAROSWITCH David s. Willard, HighRolls, N. Mex., assignor to the United States of America as representedby the Secretary of the Air Force Application February 14, 1958, SerialNo. 715,476 3 Claims. (Cl. 200-83) (Granted under Tifle 35, US. Code(1952), sec. 266) The invention described herein may be manufactured andused by or for the United States Government for governmental purposeswithout payment to me of any royalty thereon.

This invention relates to a barometric pressure responsive switch withpressure-controlled means which, as illustrated herein, prevents closureof the switch points until a predetermined altitude has been reached inascent but permits closing the contacts at a predetermined altitude ondescent.

In balloon flights carrying instruments, it is frequently desirable tohave the balloon go as high as possible and this invention would beuseful in releasing a load, which might well be attached to a parachute,after a balloon has passed a predetermined altitude and on descent againreaches the predetermined level.

It will be particularly useful, where a balloon has burst after passinga predetermined altitude, to release the load on descent and prevententanglement with the balloon debris.

It is an object of this invention to provide a simple, trouble-freemechanism which complies with a CAA requirement concerning balloonflights.

It is a further object of this invention to provide a selfarming deviceconsisting of a safety latch controlling a switch arm actuated by abarometric responsive bellows which switch arm on release, permitsclosure of contacts of a micro switch to complete an electrical circuitactuating any one of a number of conventional parachute or loadreleases.

The drawing is a cross-sectional view of the invention showing theessential elements.

The body or frame can be of any suitable metal such as aluminum. Aconventional bellows 12, which may be partially evacuated, is responsiveto barometric pressure as will later become apparent. The bellows 12 issecured in the frame 10 by a threaded stud 14 and locknut 16 and isprovided on its free end with an extension 18. A switch arm 24 ispivoted on a pin 26 and carries opposite the bellows extension 18 anadjustment screw 20 held in adjusted position by a locknut 22. Near thelower end of switch arm 24 is a slot or notch 28 which receives the freeend of a tensioned safety latch spring 30. The spring 30 is secured tothe frame 10 by suitable machine screws 32 and 34 and is provided withan adjustment screw 38 held in place by locknuts 40 and 40'. A coiledspring 36 is held under tension by adjustment screw 38 and an adjustmentscrew 42 which is threaded in the lower end of the switch arm 24. Anadjustment screw 44 is threaded in the lower end of the switch arm 24communicating with the notch 28 to adjust the depth that the end of thesafety spring 30 enters said notch 28. A micro switch 46 is fastened tothe frame 10 by a screw 48 and is provided with push button 49 and anextension 50. An extension 52 of the switch arm 24 has threaded thereinan adjustment screw 54 opposed to the micro switch extension 50 andmaintained in adjusted position Patented Apr. 21, 1959 by a loeknut 56.-Leads 58 and 60 are provided for connecting the micro switch 46 to asuitable source of electric power.

In operation, the switch arm 24 is held in the safety position shown inthe drawing by the tension ofthe spring 36 against the end of the safetylatch spring 30 which rests in the notch 28. When the device is carriedby the balloon to the predetermined altitude, which is set by adjustmentscrew 20, the expansion of the barometric bellows 12 forces the bellowsextension 18 against the screw 20 to swing the lower end of the switcharm 24 to the right. The free end of the flexed safety latch spring 30is removed from the notch 28 whence its spring action carries it to aposition below the said switch arm. This so conditions the device thatthe switch arm 24 is free to move to the left whenever the tension ofmain spring 36 is greater than the expansion force of the bellows 12. Asthe device falls to a lower level, the bellows 12 contracts and the mainspring 36 pulls the switch arm 24 to the left forcing the adjustmentscrew 54 against micro switch extension 50 closing the switch contactsand thus activating the releasing apparatus.

This invention has many features which make it invaluable for use inballoon flights. The altitude at which the safety switch can be set islimited only by the capability of the barometric bellows 12. Themechanical design is such that the invention allows adjustment to anyaltitude between sea level and excess of 70,000 feet. The safety spring30, held in position by the coiled main spring in the notch 28 of theswitch arm 24, insures stability and prevents premature operation of thedevice by accidental shock or jars in handling and in flight.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A circuit controlling device comprising a supporting frame, agas-filled bellows fixed to said frame and having a portion movablerelatively thereto in response to variations in barometric pressure, anarm pivoted in said frame for movement in response to a predeterminedbarometric pressure, a spring latch normally preventing movement of saidarm toward said bellows, spring means for normally maintaining said armand said latch in engagement until said arm is swung by said bellows inresponse to movement of said bellows upon reaching a predeterminedbarometric pressure, said spring latch being biased in a direction toprevent subsequent reengagement of said latch and arm after movement ofsaid arm in response to movement of said bellows, a circuit controllingswitch, and an extension on said arm arranged to actuate said switchwhen the biasing pressure on said arm from said biasing means exceedsthe pressure of said bellows on said arm and upon returning to saidpredetermined barometric pressure.

2. A pressure-responsive device including a self-arming deviceconsisting of a frame of any suitable metal, a bellows sensitive tobarometric pressure secured by one end thereto, an extension on the freeend of said bellows, a lever arm pivoted on said frame and having a slotin one end thereof, an adjustable screw secured in said lever armopposed to said extension on said bellows, a spring latch supported insaid slot, a spring biasing said lever arm against said spring latch andopposed to the expansion of said bellows, an extension on said leverarm, and a micro switch with a plunger arm opposed to said extension ofsaid lever arm, said micro switch to be actuated when the device hasreached or passed a predetermined altitude and on descent again reachessaid altitude.

3. In a switch sensitive to barometric pressure for actuating a devicefor releasing a load from a balloon after it has reached and passed apredetermined altitude, a

latch spring =and to permit the said lever arm to actuate said microswitch on descent to the 'prefieterrni'nee level.

References Cited inthe file of this patent UNITED STATES PATENTS Zelleretal May 25, Stadler Aug. 14, Murphy June 1.

Jim. a

